The proposal presents three separate research projects that will explore the nature of the relationship or comorbidity of psychopathology and physical disability, specifically temporomandibular disorder and low back pain disability. The major goal of the first project is to evaluate whether DSM-III-R Axis I and II diagnoses will serve as useful predictors for those acute low back pain patients who subsequently develop chronic disability problems. A conceptual model of the transition from acute to chronic pain is proposed which guides this research. This study will provide the first important statistics on the incidence of specific psychiatric and personality disorders within an exclusively acute low back pain population that may be linked with subsequent chronicity. The second project will focus on evaluating the active components of a functional restoration treatment program for chronic low back pain disability. For these chronic pain patients, significant psychopathology is often evidenced. Functional restoration has been found to be quite effective at getting these chronically disabled patients back to work. An important question still remaining is what components (both psychological and physical) are most important for treatment success. Addressing this issue may allow the development of a more time- and cost- efficient treatment program. Finally, the third proposed project will be similar to the first project, but it will target a different clinical population--patients with temporomandibular disorder (TMD). It will help test how generalizable the proposed conceptual model is of the transition from acute to chronic pain. It should be noted that chronic TMD and chronic low back pain are disabilities that have many things in common. This is why research in both areas is being simultaneously pursued. For example, there is often great difficulty unequivocally diagnosing organic underpinnings of both of these disorders. Moreover, psychological factors have been implicated to play a very important role in the etiology and maintenance of these syndromes. There have also been many psychological and physical approaches advocated for treating these disorders, although the majority have not been empirically demonstrated to be successful. In addition, there has been an increase in the apparent prevalence and perceived severity of these disorders over the past decade, making them both costly societal and economic problems. Finally, involvement in this work with TMD and chronic low back pain reveals a close relationship or comorbidity of psychopathology and these physical disabilities. These three research projects will further explore the nature of this comorbidity.